Fuel Pump Electrical Circuit Diagnosis LTD wtihout Turbocharger

The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

The following conditions may cause the fuel pump fuse to open:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 43244 Relay Puller Pliers

For equivalent regional tools, refer to Special Tools.

Note: An open or a short to voltage in the control circuit will cause both the Ckt. Open Test Status and the Ckt. Short Volts Test Status parameters to display Fault.

Ignition ON, command the fuel pump relay ON and OFF with a scan tool while observing the following control circuit status parameters:

Each parameter should toggle between OK and Not Run or Not Run and OK.

1. Ignition OFF, disconnect the fuel pump relay using the J 43244 Pliers .
2. Ignition ON, verify that a test lamp illuminates between the ground circuit terminal 85 and B+.

⇒	If the test lamp does not illuminate, test the ground circuit for a short to voltage or an open/high resistance.

3. Verify that a test lamp does not illuminate between the ground circuit terminal 85 and the control circuit terminal 86.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

4. Remove the test lamp.
5. Command the fuel pump relay ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is OK.

⇒	If not the specified value, test the fuel pump relay control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.

6. Install a 3A fused jumper wire between the fuel pump relay control circuit terminal 86 and the ground circuit terminal 85. Command the fuel pump ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is Fault.

⇒	If not the specified value, test the fuel pump relay control circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

7. Inspect the fuel pump fuse.

⇒	If the fuel pump fuse is open, test for the following conditions:

•	A short to ground in the relay switch B+ circuit

•	A short to ground in the supply voltage circuit of the fuel pump

⇒	If the above circuits test normal, replace the fuel pump module.

8. Verify that a test light illuminates between the B+ circuit terminal 30 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

9. Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the supply voltage circuit terminal 87 of the fuel pump. Verify the fuel pump is activated.

⇒	If the fuel pump does not activate, test for the following conditions:

•	An open/high resistance in the supply voltage circuit of the fuel pump

•	An open/high resistance in the ground circuit of the fuel pump

⇒	If the above circuits test normal, replace the fuel pump module.

10. If all circuits test normal, test or replace the fuel pump relay.

1. Ignition OFF, disconnect the fuel pump relay.
2. Test for 70-110Ω between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the relay.

4. Install a 15A fused jumper wire between relay terminal 85 and 12V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2Ω between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.